pm25_one_liner.sh

curl -s https://www.purpleair.com/json?show=$SENSOR_ID | jq '.results[] | .PM2_5Value' | sed -e 's/^"//' -e 's/"$//' | awk '{ total += $1; count++ } END { print total/count }'

pm25_with_label.sh

#!/usr/bin/env bash

SENSOR_ID=1 # replace this with your sensor

PM25=$(curl -s https://www.purpleair.com/json?show=$SENSOR_ID |
       jq '.results[] | .PM2_5Value' |
       sed -e 's/^"//' -e 's/"$//' |
       awk '{ total += $1; count++ } END { print int(total/count*100) }')

if [ "$PM25" -le 1200 ]; then
  LABEL="GOOD"
else
  LABEL="BAD"
fi

echo "$LABEL ($(echo "scale=2; $PM25/100" | bc -l))"